/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.manning.androidhacks.hack040;

import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.util.TypedValue;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.view.ViewTreeObserver;
import android.widget.AbsListView;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.Toast;

import com.manning.androidhacks.hack040.provider.Images;
import com.manning.androidhacks.hack040.util.ImageCache;
import com.manning.androidhacks.hack040.util.ImageCache.ImageCacheParams;
import com.manning.androidhacks.hack040.util.ImageFetcher;
import com.manning.androidhacks.hack040.util.ImageResizer;
import com.manning.androidhacks.hack040.util.Utils;

/**
 * The main fragment that powers the ImageGridActivity screen. Fairly straight
 * forward GridView implementation with the key addition being the ImageWorker
 * class w/ImageCache to load children asynchronously, keeping the UI nice and
 * smooth and caching thumbnails for quick retrieval. The cache is retained over
 * configuration changes like orientation change so the images are populated
 * quickly as the user rotates the device.
 */
public class ImageGridFragment extends Fragment implements
    AdapterView.OnItemClickListener {
  private static final String TAG = "ImageGridFragment";
  private static final String IMAGE_CACHE_DIR = "thumbs";

  private int mImageThumbSize;
  private int mImageThumbSpacing;
  private ImageAdapter mAdapter;
  private ImageResizer mImageWorker;

  /**
   * Empty constructor as per the Fragment documentation
   */
  public ImageGridFragment() {
  }

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setHasOptionsMenu(true);

    mImageThumbSize = getResources().getDimensionPixelSize(
        R.dimen.image_thumbnail_size);
    mImageThumbSpacing = getResources().getDimensionPixelSize(
        R.dimen.image_thumbnail_spacing);

    mAdapter = new ImageAdapter(getActivity());

    ImageCacheParams cacheParams = new ImageCacheParams(IMAGE_CACHE_DIR);

    // Allocate a third of the per-app memory limit to the bitmap memory cache.
    // This value
    // should be chosen carefully based on a number of factors. Refer to the
    // corresponding
    // Android Training class for more discussion:
    // http://developer.android.com/training/displaying-bitmaps/
    // In this case, we aren't using memory for much else other than this
    // activity and the
    // ImageDetailActivity so a third lets us keep all our sample image
    // thumbnails in memory
    // at once.
    cacheParams.memCacheSize = 1024 * 1024 * Utils
        .getMemoryClass(getActivity()) / 3;

    // The ImageWorker takes care of loading images into our ImageView children
    // asynchronously
    mImageWorker = new ImageFetcher(getActivity(), mImageThumbSize);
    mImageWorker.setAdapter(Images.imageThumbWorkerUrlsAdapter);
    mImageWorker.setLoadingImage(R.drawable.empty_photo);
    mImageWorker.setImageCache(ImageCache.findOrCreateCache(
        getActivity(), cacheParams));
  }

  @Override
  public View onCreateView(LayoutInflater inflater,
      ViewGroup container, Bundle savedInstanceState) {

    final View v = inflater.inflate(R.layout.image_grid_fragment,
        container, false);
    final GridView mGridView = (GridView) v.findViewById(R.id.gridView);
    mGridView.setAdapter(mAdapter);
    mGridView.setOnItemClickListener(this);

    // This listener is used to get the final width of the GridView and then
    // calculate the
    // number of columns and the width of each column. The width of each column
    // is variable
    // as the GridView has stretchMode=columnWidth. The column width is used to
    // set the height
    // of each view so we get nice square thumbnails.
    mGridView.getViewTreeObserver().addOnGlobalLayoutListener(
        new ViewTreeObserver.OnGlobalLayoutListener() {
          @Override
          public void onGlobalLayout() {
            if (mAdapter.getNumColumns() == 0) {
              final int numColumns = (int) Math.floor(mGridView
                  .getWidth() / (mImageThumbSize + mImageThumbSpacing));
              if (numColumns > 0) {
                final int columnWidth = (mGridView.getWidth() / numColumns)
                    - mImageThumbSpacing;
                mAdapter.setNumColumns(numColumns);
                mAdapter.setItemHeight(columnWidth);
                if (BuildConfig.DEBUG) {
                  Log.d(TAG, "onCreateView - numColumns set to "
                      + numColumns);
                }
              }
            }
          }
        });

    return v;
  }

  @Override
  public void onResume() {
    super.onResume();
    mImageWorker.setExitTasksEarly(false);
    mAdapter.notifyDataSetChanged();
  }

  @Override
  public void onPause() {
    super.onPause();
    mImageWorker.setExitTasksEarly(true);
  }

  @Override
  public void onItemClick(AdapterView<?> parent, View v, int position,
      long id) {
    final Intent i = new Intent(getActivity(),
        ImageDetailActivity.class);
    i.putExtra(ImageDetailActivity.EXTRA_IMAGE, (int) id);
    startActivity(i);
  }

  @Override
  public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
    inflater.inflate(R.menu.main_menu, menu);
  }

  @Override
  public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    case R.id.clear_cache:
      final ImageCache cache = mImageWorker.getImageCache();
      if (cache != null) {
        mImageWorker.getImageCache().clearCaches();
        // DiskLruCache.clearCache(getActivity(), ImageFetcher.HTTP_CACHE_DIR);
        Toast.makeText(getActivity(), R.string.clear_cache_complete,
            Toast.LENGTH_SHORT).show();
      }
      return true;
    }
    return super.onOptionsItemSelected(item);
  }

  /**
   * The main adapter that backs the GridView. This is fairly standard except
   * the number of columns in the GridView is used to create a fake top row of
   * empty views as we use a transparent ActionBar and don't want the real top
   * row of images to start off covered by it.
   */
  private class ImageAdapter extends BaseAdapter {

    private final Context mContext;
    private int mItemHeight = 0;
    private int mNumColumns = 0;
    private int mActionBarHeight = -1;
    private GridView.LayoutParams mImageViewLayoutParams;

    public ImageAdapter(Context context) {
      super();
      mContext = context;
      mImageViewLayoutParams = new GridView.LayoutParams(
          LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
    }

    @Override
    public int getCount() {
      // Size of adapter + number of columns for top empty row
      return mImageWorker.getAdapter().getSize() + mNumColumns;
    }

    @Override
    public Object getItem(int position) {
      return position < mNumColumns ? null : mImageWorker.getAdapter()
          .getItem(position - mNumColumns);
    }

    @Override
    public long getItemId(int position) {
      return position < mNumColumns ? 0 : position - mNumColumns;
    }

    @Override
    public int getViewTypeCount() {
      // Two types of views, the normal ImageView and the top row of empty views
      return 2;
    }

    @Override
    public int getItemViewType(int position) {
      return (position < mNumColumns) ? 1 : 0;
    }

    @Override
    public boolean hasStableIds() {
      return true;
    }

    @Override
    public View getView(int position, View convertView,
        ViewGroup container) {
      // First check if this is the top row
      if (position < mNumColumns) {
        if (convertView == null) {
          convertView = new View(mContext);
        }
        // Calculate ActionBar height
        if (mActionBarHeight < 0) {
          TypedValue tv = new TypedValue();
          if (mContext.getTheme().resolveAttribute(
              android.R.attr.actionBarSize, tv, true)) {
            mActionBarHeight = TypedValue.complexToDimensionPixelSize(
                tv.data, mContext.getResources().getDisplayMetrics());
          } else {
            // No ActionBar style (pre-Honeycomb or ActionBar not in theme)
            mActionBarHeight = 0;
          }
        }
        // Set empty view with height of ActionBar
        convertView.setLayoutParams(new AbsListView.LayoutParams(
            ViewGroup.LayoutParams.MATCH_PARENT, mActionBarHeight));
        return convertView;
      }

      // Now handle the main ImageView thumbnails
      ImageView imageView;
      if (convertView == null) { // if it's not recycled, instantiate and
                                 // initialize
        imageView = new ImageView(mContext);
        imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
        imageView.setLayoutParams(mImageViewLayoutParams);
      } else { // Otherwise re-use the converted view
        imageView = (ImageView) convertView;
      }

      // Check the height matches our calculated column width
      if (imageView.getLayoutParams().height != mItemHeight) {
        imageView.setLayoutParams(mImageViewLayoutParams);
      }

      // Finally load the image asynchronously into the ImageView, this also
      // takes care of
      // setting a placeholder image while the background thread runs
      mImageWorker.loadImage(position - mNumColumns, imageView);
      return imageView;
    }

    /**
     * Sets the item height. Useful for when we know the column width so the
     * height can be set to match.
     * 
     * @param height
     */
    public void setItemHeight(int height) {
      if (height == mItemHeight) {
        return;
      }
      mItemHeight = height;
      mImageViewLayoutParams = new GridView.LayoutParams(
          LayoutParams.MATCH_PARENT, mItemHeight);
      mImageWorker.setImageSize(height);
      notifyDataSetChanged();
    }

    public void setNumColumns(int numColumns) {
      mNumColumns = numColumns;
    }

    public int getNumColumns() {
      return mNumColumns;
    }
  }
}
